MEPS 572:19-42 (2017)  -  DOI:

Summer and fall distribution of phytoplankton in relation to environmental variables in Labrador fjords, with special emphasis on Phaeocystis pouchetii 

Armelle-Galine Simo-Matchim1,*, Michel Gosselin1, Michel Poulin2, Mathieu Ardyna3,4, Sylvie Lessard

1Institut des sciences de la mer de Rimouski, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada
2Recherche et collections, Musée canadien de la nature, CP 3443, Succursale D, Ottawa, Ontario K1P 6P4, Canada
3Takuvik Joint International Laboratory, Université Laval (Canada) - CNRS (France), UMI3376, Département de biologie et Québec-Océan, Université Laval, Québec, Québec G1V 0A6, Canada
4Sorbonne Universités, UPMC Univ Paris 06, INSU-CNRS, Laboratoire d’Océanographie de Villefranche, 181 Chemin du Lazaret, 06230 Villefranche-sur-mer, France
Corresponding author:

ABSTRACT: Protist (>2 µm) taxonomic composition was investigated for the first time in 4 Labrador fjords (Nachvak, Saglek, Okak and Anaktalak) during summers 2007 and 2013, early fall 2010 and late fall 2009. Protist composition was significantly different from one season to another. Significant spatial differences in protist composition were found only during summer 2013. During summer 2007, the community was characterized by diatoms and a mixed assemblage of flagellates. In summer 2013, flagellates largely dominated the community, and an intense Phaeocystis pouchetii bloom was observed in Nachvak Fjord (18 × 106 cells l-1). In autumn, the community was dominated by unidentified flagellates, prymnesiophytes and diatoms, in various proportions from early to late fall. From a summer situation characterized by stronger stratification, higher incident irradiance and depleted nutrients in surface waters, it evolved to an autumn situation characterized by decreasing air temperature and irradiance associated with an environmental forcing (e.g. weather) allowing cooling and greater vertical mixing of the water column. Combining our observations with those from the literature, we suggest the following annual succession in the Labrador fjord phytoplankton community: (winter) dinoflagellates and small flagellated cells—(spring) Fragilariopsis spp., Chaetoceros spp., Thalassiosira spp. and Phaeocystis pouchetii—(summer) Chaetoceros spp., P. pouchetii and Chrysochromulina spp.—(fall) Gymnodinium/Gyrodinium spp., Chrysochromulina spp. and other flagellates. Overall, the protist richness was 2 times higher in fall than in summer, the highest richness being observed in early fall, with 201 taxonomic entries, 72 genera and 131 species identified.

KEY WORDS: Taxonomic composition · Protists · Phytoplankton · Diatoms · Phaeocystis · Seasonal variability · Northeastern Canada · Labrador · Fjords

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Cite this article as: Simo-Matchim AG, Gosselin M, Poulin M, Ardyna M, Lessard S (2017) Summer and fall distribution of phytoplankton in relation to environmental variables in Labrador fjords, with special emphasis on Phaeocystis pouchetii . Mar Ecol Prog Ser 572:19-42.

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